Semiconductor device

ABSTRACT

A seal ring structure is formed through a multilayer structure of a plurality of dielectric films in a peripheral part of a chip region to surround the chip region. A dual damascene interconnect in which an interconnect and a plug connected to the interconnect are integrated is formed in at least one of the dielectric films in the chip region. Part of the seal ring structure formed in the dielectric film in which the dual damascene interconnect is formed is continuous. A protection film formed on the multilayer structure has an opening on the seal ring. A cap layer connected to the seal ring is formed in the opening.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.13/551,425, filed Jul. 17, 2012, which is a Divisional of U.S. patentapplication Ser. No. 13/171,181, filed on Jun. 28, 2011, now U.S. Pat.No. 8,247,876, which is a Divisional of U.S. patent application Ser. No.12/858,942, filed on Aug. 18, 2010, now U.S. Pat. No. 7,994,589, whichis a Divisional of U.S. patent application Ser. No. 12/264,675, filed onNov. 4, 2008, now U.S. Pat. No. 7,948,039, which is a Divisional of U.S.patent application Ser. No. 10/983,760, filed on Nov. 9, 2004, now U.S.Pat. No. 7,453,128, claiming priority of Japanese Patent Application No.2003-379754 filed on Nov. 10, 2003, whose priority is claimed under 35USC §119, the disclosures of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device having a sealring structure surrounding a chip region and to a method for fabricatingthe device.

A semiconductor device is generally fabricated by arranging a largenumber of integrated circuits (ICs) constituted by a plurality ofelements and provided with given functions on a semiconductor wafer of,for example, silicon.

A large number of chip regions arranged on a wafer are separated fromeach other by a scribe region (scribe line) having a lattice pattern.After the large number of chip regions have been formed on a waferthrough a semiconductor fabrication process, the wafer is diced intochips along the scribe region, thereby forming semiconductor devices.

However, when the wafer is diced into chips, chip regions near thescribe line might suffer mechanical damage, resulting in occurrence ofcracks or chipping in part of the diced cross sections of the separatedchips, i.e., semiconductor devices.

To solve this problem, in Japanese Unexamined Patent Publication (Kokai)No. 2001-23937 (hereinafter, referred to as reference 1), proposed is atechnique for preventing crack propagation in chip regions during dicingby providing a seal ring serving as a ring-shaped protection wall aroundthe chip regions.

FIG. 19 is a cross-sectional view showing a conventional semiconductordevice (formed in a wafer) having a seal ring.

As shown in FIG. 19, a chip region 2 is defined in a substrate 1 of awafer by a scribe region 3. A multilayer structure made of a pluralityof interlayer dielectric films 5 through 10 is formed on the substrate1. An active layer 20 constituting an element is formed in the substrate1 in the chip region 2. A plug (via) 21 is formed through the interlayerdielectric film 5 to be connected to the active layer 20. Aninterconnect 22 is formed through the interlayer dielectric film 6 to beconnected to the plug 21. A plug 23 is formed through the interlayerdielectric film 7 to be connected to the interconnect 22. An tointerconnect 24 is formed through the interlayer dielectric film 8 to beconnected to the plug 23. A plug 25 is formed through the interlayerdielectric film 9 to be connected to the interconnect 24. Aninterconnect 26 is formed through the interlayer dielectric film 10 tobe connected to the plug 25.

As shown in FIG. 19, in part of the multilayer structure of theinterlayer dielectric films 5 through 10 located in a peripheral part ofthe chip region 2, a seal ring 4 is formed through the multilayerstructure to completely surround the chip region 2. As shown inreference 1, for example, the seal ring 4 is formed by alternately usingmasks for forming interconnects and masks for forming vias.Specifically, the seal ring 4 includes: a conductive layer 30 formed inthe substrate 1; a seal via 31 formed through the interlayer dielectricfilm 5 to be connected to the conductive layer 30; a seal interconnect32 formed through the interlayer dielectric film 6 to be connected tothe seal via 31; a seal via 33 formed through the interlayer dielectricfilm 7 to be connected to the seal interconnect 32; a seal interconnect34 formed through the interlayer dielectric film 8 to be connected tothe seal via 33; a seal via 35 formed through the interlayer dielectricfilm 9 to be connected to the seal interconnect 34; and a sealinterconnect 36 formed through the interlayer dielectric film 10 to beconnected to the seal via 35. Parts of the seal ring formed by usingmasks for forming interconnects will be hereinafter referred to as sealinterconnects, and parts of the seal ring formed by using masks forforming vias will be hereinafter referred to as seal vias.

As shown in FIG. 19, a passivation film 11 is formed on the multilayerstructure of the interlayer dielectric films 5 through 10 in whichinterconnects (22, 24, 26), vias (21, 23, 25) and the seal ring 4 areprovided. The passivation film 11 has an opening on the interconnect 26,and a pad 27 connected to the interconnect 26 is formed in the opening.

SUMMARY OF THE INVENTION

However, the conventional semiconductor device has the problem that thepassivation film peels off by impact caused during dicing of a wafer orthe problem that the impact propagates through the passivation film toreach the inside of the chip region.

If the passivation film has an opening on the seal ring and the upperpart of the seal ring is exposed in the opening as in the semiconductordevice disclosed in reference 1, it is impossible to sufficientlyprevent moisture or the like from entering a region surrounded by theseal ring from the outside.

To prevent increase in capacitance between interconnects involved inminiaturization of semiconductor elements and of interconnects connectedthereto, i.e., to prevent decrease in processing speed of semiconductordevices, a technique for preventing the increase in capacitance betweeninterconnects by using interlayer dielectric films with low dielectricconstants (low-κ interlayer dielectric films) has been developed.

However, the low-κ interlayer dielectric films generally have lowmechanical strength, so that the low-κ interlayer dielectric filmsexhibit insufficient durability against stress occurring during dicing,as compared to interlayer dielectric films made of conventionalmaterials. Therefore, the low-κ interlayer dielectric films aresusceptible to damage during dicing. Accordingly, even if a seal ring isformed by alternately using masks for vias and masks for interconnectsin a peripheral part of a chip region in a semiconductor device usingsuch low-κ interlayer dielectric films as in the conventional device,damage during dicing is not sufficiently prevented. Specifically, theconventional seal ring formed by alternately using masks for vias andmasks for interconnects includes a large number of components, so thatthe seal ring has a large number of junctions between components (e.g.,a junction between a seal via and a seal interconnect). As the number ofjunctions between components increases, the number of portions wherecomponents are not connected is likely to increase. As a result, suchjunctions (or portions where components are not connected) act as pathsthrough which impact propagates, so that it is impossible to preventcracks or the like occurring during dicing from propagating into chipregions.

It is therefore an object of the present invention to preventdegradation of moisture resistance and reliability of a semiconductordevice by preventing propagation of chipping, cracks and the like causedduring dicing, which is performed to divide a wafer into chips, from aside of a chip (semiconductor device) into a chip region.

In order to obtain the object, a semiconductor device according to thepresent invention includes: an element formed on a substrate in a chipregion; a multilayer structure including a plurality of interlayerdielectric films formed on the substrate; an interconnect formed in atleast one of the interlayer dielectric films in the chip region; a plugformed in at least one of the interlayer dielectric films in the chipregion and connecting either the element and the interconnect or theinterconnect and another interconnect; a seal ring structure formedthrough the multilayer structure in a peripheral part of the chip regionand surrounding the chip region (without interruption); and a protectionfilm formed on the multilayer structure in which the interconnect, theplug and the seal ring structure are provided. In this device, a dualdamascene interconnect in which the interconnect and the plug connectedto the interconnect are integrated is formed in at least one of theinterlayer dielectric films in the chip region, part of the seal ringstructure located in the interlayer dielectric film in which the dualdamascene interconnect is formed is continuous, and the protection filmhas an opening on the seal ring structure, and a cap layer connected tothe seal ring structure is formed in the opening.

In the semiconductor device of the present invention, the protectionfilm such as a passivation film has an opening on the seal ringstructure. In other words, the protection film is partiallydiscontinuous in a peripheral part of the chip region. Accordingly, itis possible to prevent peeling of the protection film in the chip regioncaused by impact on a wafer during dicing. It is also possible toprevent impact on the protection film outside the chip region frompropagating through the protection film and reaching the inside of thechip region.

In addition, at least part of the seal ring structure is continuous inthe interlayer dielectric film in which the dual damascene structure isprovided. In other words, this part of the seal ring structure has no“junction.” Accordingly, the number of “junctions” between components inthe entire seal ring structure is reduced. As a result, it is possibleto prevent cracks or the like occurring during dicing from propagatinginto the chip region through “junctions.” It is also possible to preventan impurity or the like from entering the chip region from the outsideof the seal ring structure.

Moreover, the cap layer (e.g., a cap layer made of a conductor) isburied in the opening of the protection film formed on the seal ringstructure such that this cap layer and the body of the seal ringstructure are continuous. Accordingly, unlike a case where no cap layeris provided, it is possible to prevent moisture or an impurity which hasentered from the scribe region during dicing from entering the chipregion via the peripheral part of the chip region, i.e., the opening ofthe protection film near the scribe region.

In the device of the present invention, at least part of the seal ringstructure is preferably buried in a concave portion formed in one of theinterlayer dielectric films or in at least two successive interlayerdielectric films out of the plurality of interlayer dielectric films,and the concave portion preferably has an aspect ratio of three or more.

This ensures reduction of the number of “junctions” between componentsin the entire seal ring structure.

In the device of the present invention, the seal ring structure ispreferably divided into at least two branches in at least one of theinterlayer dielectric films.

Then, a structure in which components of the seal ring structure areconnected to each other via two or more branches (which are alsocomponents of the seal ring structure) is implemented. Specifically, thechip region is surrounded by this partial structure including two (orthree or more) seal ring branches in a film. In this film, the seal ringstructure is composed of a plurality of branches, so that the seal ringstructure has high mechanical strength. Accordingly, even if aninterlayer dielectric film in the scribe region is damaged by stressoccurring during dicing, the seal ring structure serves as a protectionwall and prevents propagation of the damage to the interlayer dielectricfilm in the scribe region toward the chip region or prevents propagationof impact during dicing through the interlayer dielectric film in thechip region.

In the device of the present invention, the seal ring structurepreferably includes at least two seal rings surrounding the chip region.

Then, a first seal ring (inner seal ring) which surrounds the chipregion and at least one seal ring (outer seal ring) which surrounds thefirst seal ring and is electrically insulated from the first seal ringare formed between the chip region and the scribe region surrounding thechip region. With this structure, even if a seal ring located outsidethe first seal ring is damaged, e.g., suffered from breaking or cracks,by the stress from a dicing blade during dicing, the first seal ringprevents impact from propagating into the chip region. Even if the sealring outside the first seal ring is damaged, the first seal ringprevents moisture or a contaminant from entering the chip region becausethe first seal ring is formed independently of this outer seal ring.

If the chip region is surrounded by at least two seal rings, the openingof the protection film may be located only on an outermost seal ring outof the seal rings, and the cap layer may be formed in the opening to beconnected to the outermost seal ring. Alternatively, each of the sealrings may be divided into at least two branches in at least one of theinterlayer dielectric films.

In the device of the present invention, a plurality of projections arepreferably provided on a side of the seal ring structure.

Then, it is possible to prevent impact and stress caused by contact of adicing blade with a film such as a protection film during dicing of awafer and cracks and the like occurring in the wafer resulting from theimpact and stress, from propagating along the side (the side facing thescribe region) of the seal ring structure.

In the device of the present invention, the seal ring structurepreferably has a waved-shaped periphery when viewed from above thesubstrate.

Then, it is possible to prevent impact and stress caused by contact of adicing blade with a film such as a protection film during dicing of awafer and cracks and the like occurring in the wafer resulting from theimpact and stress, from propagating along the side of the seal ringstructure.

In the device of the present invention, the seal ring structure mayinclude at least one material selected from the group consisting of W,Al and Cu.

In the semiconductor device of the present invention, if the cap layerincludes Al, prevention of erosion of the seal ring structure(especially a seal ring structure made of Cu) is ensured.

A method for fabricating a semiconductor device according to the presentinvention is a method for fabricating a semiconductor device including:an element formed on a substrate in a chip region; a multilayerstructure including a plurality of interlayer dielectric films formed onthe substrate; an interconnect formed in at least one of the interlayerdielectric films in the chip region; a plug formed in at least one ofthe interlayer dielectric films in the chip region and connecting eitherthe element and the interconnect or the interconnect and anotherinterconnect; and a seal ring structure formed through the multilayerstructure in a peripheral part of the chip region and surrounding thechip region. Specifically, the method includes the steps of: forming,through one of the interlayer dielectric films, a first concave portionin which the plug is to be buried and a second concave portion in whichpart of the seal ring structure is to be buried; forming a third concaveportion in which the interconnect is to be buried in an upper part ofsaid one of the interlayer dielectric films such that the third concaveportion is connected to the first concave portion; burying a conductivefilm in the first, second and third concave portions, thereby forming adual damascene interconnect in which the plug and the interconnect areintegrated and said part of the seal ring structure; forming aprotection film on the multilayer structure in which the interconnect,the plug and the seal ring structure are provided; and forming anopening in part of the protection film on the seal ring structure andforming a cap layer in the opening such that the cap layer is connectedto the seal ring structure.

That is, the method for fabricating a semiconductor device according tothe present invention is a method for fabricating the above-describedsemiconductor device. Therefore, the same advantages are obtained.

In the method of the present invention, if the aspect ratio of thesecond concave portion is three or more, reduction of the number of“junctions” between components in the entire seal ring structure isensured.

The method of the present invention may further include the step offorming a fourth concave portion in which another part of the seal ringstructure is to be buried in another interlayer dielectric film stackedon said one of the interlayer dielectric films such that the fourthconcave portion is connected to the second concave portion.

As described above, according to the present invention, in asemiconductor device including a chip region and a seal ring structureprovided in a peripheral part of the chip region and surrounding anelement, interconnect layers and others in the chip region, a seal ringstructure including a small number of “junctions” between its componentsis provided, a protection film has an opening on the seal ringstructure, and a cap layer is formed in the opening. This seal ringstructure may partially include branches (e.g., at least two conductorsserving as bridges in part of the seal ring structure) or may includetwo or more seal rings surrounding the chip region (e.g., a first sealring formed in a peripheral part of the chip region and at least oneseal ring surrounding the first seal ring.)

With the foregoing features of the present invention, it is possible toprevent chipping, breaking and the like caused by dicing a wafer intochips (semiconductor devices) from reaching chip regions. Accordingly,it is also possible to prevent degradation of the moisture resistanceand reliability of the semiconductor devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing part of a wafer on which a semiconductordevice according to a first embodiment of the present invention isprovided.

FIGS. 2A and 2B are views respectively showing variations of thecross-sectional structure taken along the line A-A′ in FIG. 1 (i.e.,cross-sectional structure of an end of a semiconductor device includinga seal ring portion located in a peripheral part of a chip region.)

FIG. 3A is a view showing a variation of the cross-sectional structuretaken along the line A-A′ in FIG. 1 (i.e., a cross-sectional structureof an end of a semiconductor device including a seal ring portionlocated in a peripheral part of a chip region.) FIG. 3B schematicallyshows planar structures of a via and a seal via provided in a film wherethe via is formed in the structure shown in FIG. 2A or 2B.

FIGS. 4A through 4D are cross-sectional views showing respective processsteps of a method for fabricating a semiconductor device according tothe first embodiment.

FIGS. 5A through 5C are cross-sectional views showing respective processsteps of the method for fabricating the semiconductor device of thefirst embodiment.

FIGS. 6A through 6C are cross-sectional views showing respective processsteps of the method for fabricating the semiconductor device of thefirst embodiment.

FIG. 7 is a plan view showing part of a wafer on which a semiconductordevice according to a second embodiment of the present invention isprovided.

FIGS. 8A and 8B are views respectively showing variations of thecross-sectional structure taken along the line B-B′ in FIG. 7 (i.e.,cross-sectional structure of an end of a semiconductor device includinga seal ring portion located in a peripheral part of a chip region.)

FIGS. 9A through 9D are cross-sectional views showing respective processsteps of a method for fabricating a semiconductor device according tothe second embodiment.

FIGS. 10A through 10C are cross-sectional views showing respectiveprocess steps of the method for fabricating the semiconductor device ofthe second embodiment.

FIG. 11A is a plan view of the semiconductor device of the secondembodiment when viewed from above. FIG. 11B is a cross-sectional view ofa chip surface taken along the line C-C′ in FIG. 11A.

FIG. 12A is a cross-sectional view showing a semiconductor deviceaccording to a first modified example of the second embodiment. FIG. 12Bis a cross-sectional view showing a semiconductor device according to asecond modified example of the second embodiment.

FIG. 13 is a cross-sectional view showing a semiconductor deviceaccording to a third modified example of the second embodiment.

FIG. 14A is a view schematically showing a cross-sectional structure ofa conventional semiconductor device shown in FIG. 19. FIG. 14B is a planview corresponding to the structure shown in FIG. 14A.

FIG. 15A is a view schematically showing a cross-sectional structure ofthe semiconductor device of the first embodiment shown in FIG. 2A. FIG.15B is a plan view corresponding to the structure shown in FIG. 15A.

FIGS. 16A through 16C are plan views respectively showing variations ofa semiconductor device according to a third embodiment of the presentinvention.

FIG. 17A is a view schematically showing a cross-sectional structure ofthe semiconductor device of the second embodiment shown in FIG. 8A. FIG.17B is a plan view corresponding to the structure shown in FIG. 17A.

FIGS. 18A through 18C are plan views respectively showing variations ofthe semiconductor device of the third embodiment.

FIG. 19 is a cross-sectional view showing the conventional semiconductordevice.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the drawings.

A first feature of the present invention is that a seal ring and aninterconnect structure are formed by the same process and a dualdamascene process is adopted to form the seal ring. Accordingly, theresultant seal ring includes a small number of “junctions” between itscomponents, as compared to the case of adopting a single damasceneprocess. In this description, a structure in which an interconnect and aplug (for connecting interconnects or an interconnect and an element)are stacked is referred to as an interconnect structure.

A second feature of the present invention is that an opening is formedin part of a passivation film (e.g., a SiN film) covering the top of theseal ring and a cap is provided in the opening. This prevents impact onthe passivation film during dicing from propagating into a chip region(see first embodiment.)

A third feature of the present invention is that the seal ring ispartially divided into two or more branches and these branches serve asan integrated unit. This enhances the mechanical strength of the sealring itself, thereby preventing impact from a scribe line during dicingfrom propagating into a chip region.

A fourth feature of the present invention is that at least two sealrings surround a chip region. Accordingly, the seal ring structure isstronger than a seal ring structure in which a single seal ringsurrounds the chip region (see second embodiment.)

The other embodiments of the present invention will be specificallydescribed in the following description.

Embodiment 1

Hereinafter, a semiconductor device and a method for fabricating thedevice according to a first embodiment of the present invention will bedescribed with reference to drawings.

FIG. 1 is a plan view showing part of a wafer on which the semiconductordevice of the first embodiment (i.e., a semiconductor device in whichone seal ring surrounds a chip region) is provided.

As shown in FIG. 1, on a wafer 101 to be a semiconductor substrate,which is typically a silicon substrate, for example, a plurality of chipregions 102 to be semiconductor devices are provided. In each of thechip regions 102, an integrated circuit (IC) made of a plurality ofelements and provided with a given function is formed. The chip regions102 are defined by a scribe region 103 having a lattice pattern.

A semiconductor device (i.e., a semiconductor chip) includes: a chipregion 102 on which an IC made of a plurality of elements and providedwith a given function is formed; and a seal ring 104 provided in aperipheral part of the chip region 102 to surround the chip region 102.The wafer 101 on which a plurality of such semiconductor devices areformed is diced along the scribe region 103, thereby separating thesemiconductor devices.

FIGS. 2A, 2B and 3A show variations of the cross-sectional structuretaken along the line A-A′ in FIG. 1 (i.e., a cross-sectional structureof an end of a semiconductor device including a seal ring portionlocated in a peripheral part of the chip region 102.) FIG. 3Bschematically shows planar structures of a via and a seal via which areprovided in the same film in the structure shown in FIG. 2A or 2B.

FIGS. 2A, 2B and 3A show cross-sectional structures of interconnectstructures and seal rings in the chip region 102.

As shown in FIGS. 1, 2A, 2B and 3A, a semiconductor device before dicingincludes the chip regions 102 and the scribe region 103, and the sealring 104 is formed in each of the chip regions 102 near the boundarybetween the chip region 102 and the scribe region 103.

Now, features of the respective structures shown in FIGS. 2A, 2B and 3Awill be described specifically.

First, the structure shown in FIG. 2A has a feature in which seal viasconstituting the seal ring 104 are continuously formed through at leasttwo films.

Next, the structure shown in FIG. 2B has a feature in which seal viasand seal interconnects constituting the seal ring 104 are alternatelyprovided.

Then, the structure shown in FIG. 3A has a feature in which a seal viaconstituting the seal ring 104 is divided into at least two branches inthe same interlayer dielectric film.

On the other hand, the structures shown in FIGS. 2A, 2B and 3A have acommon to feature in which a seal ring cap (a cap layer 125) is providedat the top of the seal ring 104.

Hereinafter, a method for fabricating a semiconductor device having thestructure shown in FIG. 2A will be described with reference to FIGS. 4Athrough 4D, 5A through 5C and 6A through 6C.

First, as shown in FIG. 4A, an active layer 110 constituting an elementsuch as a transistor is formed in a wafer 101 (hereinafter, referred toas a substrate 101) in a chip region 102. At the same time, a conductivelayer 120 configured in the same manner as the active layer 110 isformed in the substrate 101 in a peripheral part of the chip region 102(i.e., in a region to be a seal ring, which will be hereinafter referredto as a seal ring region, near a scribe region 103.)

Then, a first interlayer dielectric film 105 is deposited on thesubstrate 101. Thereafter, through a lithography process and a dryetching process, a via hole 105 a for forming a first via 111 (see FIG.4B) is formed through the first interlayer dielectric film 105 in thechip region 102 and, at the same time, a trench concave portion 105 bfor forming a first seal via 121 (see FIG. 4B) is formed through thefirst interlayer dielectric film 105 in the seal ring region. The sealvia is a component constituting a seal ring and is formed by filling thetrench concave portion with a conductive material. That is, a seal viahas a line structure having substantially the same width as that of avia in the chip region (see FIG. 3B.)

In this embodiment, the aspect ratio of the seal via (i.e., the ratio ofthe depth to the width in the concave portion in which the seal via isburied) is preferably one or more.

In this embodiment, the via hole 105 a and the trench concave portion105 b for forming the first seal via 121 are formed at the same time inthe first interlayer dielectric film 105 in the chip region 102.Alternatively, the via hole 105 a and the trench concave portion 105 bmay of course be formed individually.

Next, as shown in FIG. 4B, the via hole 105 a and the trench concaveportion 105 b formed through the first interlayer dielectric film 105are filled with a conductive film made of, for example, W (tungsten) by,for example, a chemical vapor deposition (CVD) process. Then, anunnecessary part of the conductive film extending off the via hole 105 aand the trench concave portion 105 b is removed by, for example, achemical/mechanical polishing (CMP) process, thereby forming a first via111 connected to the active layer 110 and a first seal via 121 connectedto the conductive layer 120.

Thereafter, a second interlayer dielectric film 106 is deposited on thefirst interlayer dielectric film 105. Then, through a lithographyprocess and a dry etching process, an interconnect trench 106 a forforming a first interconnect 112 (see FIG. 4C) is formed through thesecond interlayer dielectric film 106 in the chip region 102, and at thesame time, an interconnect trench 106 b for forming a first sealinterconnect 122 (see FIG. 4C) is formed through the second interlayerdielectric film 106 in the seal ring region.

Then, as shown in FIG. 4C, the interconnect trenches 106 a and 106 bformed through the second interlayer dielectric film 106 are filled witha conductive film of, for example, Cu (copper) by, for example, anelectroplating process. Then, part of the conductive film extending offthe interconnect trenches 106 a and 106 b is removed by, for example, aCMP process, thereby forming a first interconnect 112 connected to thefirst via 111 and a first seal interconnect 122 connected to the firstseal via 121.

Thereafter, as shown in FIG. 4D, a third interlayer dielectric film 107is deposited on the second interlayer dielectric film 106, and then avia hole 107 a for forming a second via 113 (see FIG. 5C) is formedthrough the third interlayer dielectric film 107 in the chip region 102.At the same time, a trench concave portion 107 b for forming a secondseal via 123 (see FIG. 5C) is formed through the third interlayerdielectric film 107 in the seal ring region. In this embodiment, apremium is placed on efficiency, and the via hole 107 a for forming thesecond via 113 to be a plug for connecting interconnects and the trenchconcave portion 107 b for forming the second seal via 123 to be a partof the seal ring 104 are formed by the same process. Alternatively, thevia hole 107 a and the trench concave portion 107 b may be formed bydifferent processes.

Subsequently, as shown in FIG. 5A, a resist film 130 for forming aninterconnect trench in which a second interconnect 114 (see FIG. 5C) isto be buried is formed on the third interlayer dielectric film 107 usinga lithography process. This resist film 130 has an opening in a regionwhere an interconnect is to be formed (hereinafter, referred to as aninterconnect region) including the via hole 107 a. The resist film 130is also buried in the trench concave portion 107 b.

Then, as shown in FIG. 5B, through a dry etching process using theresist film 130 as a mask, an interconnect trench 107 c for forming thesecond interconnect 114 is formed in an upper part of the thirdinterlayer dielectric film 107 in the chip region 102 to be connected tothe via hole 107 a. Thereafter, the remaining resist film 130 is removedby ashing.

Subsequently, as shown in FIG. 5C, a conductive film made of, forexample, Cu is buried in the via hole 107 a, the interconnect trench 107c and the trench concave portion 107 b formed in the third interlayerdielectric film 107. Then, part of the conductive film extending off theinterconnect trench 107 c and the trench concave portion 107 b (i.e.,part of the conductive film located above the third interlayerdielectric film 107) is removed by, for example, a CMP process. In thismanner, a second via 113 connected to the first interconnect 112 and asecond interconnect 114 connected to the second via 113 are formed(i.e., a dual damascene interconnect constituted by the second via 113and the second interconnect 114 is formed) in the third interlayerdielectric film 107 in the chip region 102. At the same time, a secondseal via 123 connected to the first seal interconnect to 122 is formedthrough the third interlayer dielectric film 107 in the seal ringregion. The process of forming a via and an interconnect by burying aconductive film in a concave portion as described above is generallycalled a dual damascene process.

In the case of forming the second via 113 and the second interconnect114 by a single damascene process, different conductive films are buriedin the via hole 107 a for forming the second via 113 and theinterconnect trench 107 c for forming the second interconnect 114,respectively. Therefore, two processes of burying the conductive filmsare also performed on the trench concave portion 107 b. These twoburying processes cause a “junction” inside the second seal via 123.

However, in this embodiment, the second seal via 123 is formed byburying a conductive film only once simultaneously with the formation ofan interconnect with a dual damascene structure, so that no junctionbetween conductive films occurs inside the second seal via 123.

In the case where an interconnect with a dual damascene structure isformed in an interlayer dielectric film in the chip region 102 and aseal via constituting the seal ring 104 is formed in this interlayerdielectric film as in this embodiment, the seal via has an aspect ratioof three or more. Accordingly, the number of junctions betweencomponents of the seal ring 104 is reduced, so that the seal ringfurther ensures prevention of contamination of the chip region 102 fromthe outside.

Subsequently, as shown in FIG. 6A, a fourth interlayer dielectric film108 is deposited on the third interlayer dielectric film 107, and then adual damascene interconnect structure and a seal ring are formed in thefourth interlayer dielectric film 108 by a dual damascene process, inthe same manner as the process steps shown in FIGS. 4D through 5C.

Specifically, as shown in FIG. 6A, through a lithography process and adry etching process, a via hole 108 a for forming a third via 115 (seeFIG. 6B) is formed through the fourth interlayer dielectric film 108 inthe chip region 102 and, at the same time, a trench concave portion 108b for forming a third seal via 124 is formed through the fourthinterlayer dielectric film 108 in the seal ring region. Thereafter, aresist film (not shown) for forming an interconnect trench in which athird interconnect 116 (see FIG. 6B) is to be buried is formed on thefourth interlayer dielectric film 108 using a lithography process. Thisresist film has an opening on the interconnect region including the viahole 108 a. The resist film is also buried in the trench concave portion108 b. Then, through a dry etching process using the resist film as amask, an interconnect trench 108 c for forming the third interconnect116 is formed in an upper part of the fourth interlayer dielectric film108 in the chip region 102 to be connected to the via hole 108 a. Then,the remaining resist film is removed by ashing. In this manner, aconcave portion (i.e., the via hole 108 a and the interconnect trench108 c) for forming a dual damascene interconnect and a trench concaveportion 108 b for forming the third seal via 124 are formed in thefourth interlayer dielectric film 108.

Subsequently, as shown in FIG. 6B, a conductive film made of, forexample, Cu is buried in a concave portion with the dual damascenestructure in which the via hole 108 a for forming the third via 115 andthe interconnect trench 108 c for forming the third interconnect 116 areintegrated and also buried in the trench concave portion 108 b forforming the third seal via 124. Then, part of the conductive filmextending off the interconnect trench 108 c and the trench concaveportion 108 b (i.e., part of the conductive film located above thefourth interlayer dielectric film 108) is removed by, for example, a CMPprocess. In this manner, a third via 115 connected to the secondinterconnect 114 and a third interconnect 116 connected to the third via115 are formed (i.e., a dual damascene interconnect constituted by thethird via 115 and the third interconnect 116 is formed) in the fourthinterlayer dielectric film 108 in the chip region 102. At the same time,a third seal via 124 connected to the second seal via 123 is formedthrough the fourth interlayer dielectric film 108 in the seal ringregion.

Thereafter, as shown in FIG. 6B, on the fourth interlayer dielectricfilm 108, which is the uppermost interconnect layer, a passivation film109 serving as a protection film of this uppermost interconnect layer isdeposited. Then, parts of the passivation film 109 on the thirdinterconnect 116 and the third seal via 124, respectively, are removedby a lithography process and a dry etching process, thereby formingopenings. The opening of the passivation film 109 on the third seal via124 is in the shape of a trench completely surrounding the chip region102.

Thereafter, as shown in FIG. 6C, an Al (aluminum) film, for example, isdeposited by, for example, a spattering process over the entire surfaceof the passivation film 109 including the openings on the thirdinterconnect 116 and the third seal via 124, respectively, and then thisAl film is patterned into a predetermined shape by a lithography processand a dry etching process. Specifically, an unnecessary part of the Alfilm on the region except for the openings and their neighboringportions is removed. In this manner, a pad electrode 117 connected tothe third interconnect 116 is formed in the opening of the passivationfilm 109 on the third interconnect 116 and a cap layer 125 connected tothe third seal via 124, i.e., the seal ring 104, is formed in theopening of the passivation film 109 on the third seal via 124. In thismanner, an interconnect structure and a bonding pad (pad electrode 117)for connecting the interconnect structure to an external electrode areformed in the chip region 102, whereas the seal ring 104 including thecap layer 125 at its top is formed in the seal ring region, i.e., in aperipheral part of the chip region 102.

As described above, in this embodiment, an interconnect structure isformed by using a dual damascene process with which a conductive film isburied in a hole for forming a via and a trench for forming aninterconnect at the same time. This interconnect structure and a sealvia constituting a seal ring are formed in the same process.Specifically, simultaneously with burying of a conductive film in aninterconnect trench having a dual damascene structure in which a concaveportion for forming a via and an interconnect trench for forming aninterconnect are integrated, the conductive film is also buried in aconcave portion for forming a seal via. Accordingly, a seal via having asufficient height, i.e., a seal via whose aspect ratio of the depth(height) to the width, for example, is one or more (preferably three ormore), is formed through one burying process.

Therefore, in this embodiment, the resultant seal ring has a smallernumber of “junctions” originating from burying of conductive films, ascompared to the case of forming an interconnect by a single damasceneprocess. Specifically, a merit of a small number of processes of buryingconductive films is that the number of interfaces between the conductivefilms constituting a seal ring is reduced. That is, discontinuousportions due to poor burying of conductive films are less likely tooccur between components of a seal ring, resulting in that the resultantseal ring has higher reliability than that obtained through a largenumber of burying processes.

In this embodiment, the cap layer 125 connected to the top of the sealring 104 is formed simultaneously with the formation of a pad (padelectrode 117) for supplying power from the outside to interconnectlayers in the chip region 102 or for taking a signal from theinterconnect layers to the outside. This makes it possible to form thecap layer 125 at the top of the seal ring 104 without an additionalprocess for forming the cap layer.

Hereinafter, a seal ring structure of this embodiment shown in FIG. 2Awill be described specifically.

As shown in FIG. 2A (or FIG. 6C), the seal ring of this embodiment isformed in the chip region 102 near the boundary between the chip region102 and the scribe region to 103. An element (not shown) such as atransistor is formed on the substrate 101 in the chip region 102, and aplurality of interconnect layers are formed over the element such as atransistor.

As shown in FIG. 2A, in the peripheral part of the chip region 102 asdescribed above, the seal ring 104 as a combination of the conductivelayer 120, the seal vias 121, 123 and 124 and the seal interconnect 122is formed to surround the inside of the chip region 102, i.e., theabove-mentioned element and interconnect layers and to penetrate themultilayer structure made of a plurality of interlayer dielectric films105 through 108. Specifically, the seal ring 104 is made of a conductor(e.g., Cu) continuously buried from the lowermost interlayer dielectricfilm through the uppermost interlayer dielectric film withoutinterruption (without gaps) in the multilayer structure in theperipheral part of the chip region 102 (i.e., in the chip region 102near the boundary between the chip region 102 and the scribe region103.) This seal ring 104 serves as a barricade for blocking the passageof entering of an impurity and the like from the outside into the chipregion 102.

In this embodiment, at least one conductor (component) out of stackedconductors constituting the seal ring 104 and an interconnect with adual damascene structure are formed by the same process as describedabove. Accordingly, this conductor serves as a seal via penetrating atleast one interlayer dielectric film without a “junction”. That is, theseal ring 104 is formed in the process for forming a dual damasceneinterconnect in the entire chip region 102 in which a seal ring, anelement such as a transistor, an interconnect and others are formed, sothat the number of “junctions” in the seal ring 104 is reduced. If a“junction”, i.e., an interface between conductive films serving ascomponents, is present in the seal ring, this “junction” serves as apath through which impact caused during, for example, dicing of thesubstrate (wafer) 101 along the scribe region 103 or moisture enteringfrom the outside easily propagates into the chip region 102. However, inthis embodiment, the number of “junctions” between components of theseal ring 104 is reduced, so that it is possible to prevent impactduring wafer dicing or moisture from the outside from entering the chipregion 102.

In this embodiment, the seal ring 104 is formed in the peripheral partof the chip region 102 (in the chip region 102 near the boundary betweenthe chip region 102 and the scribe region 103). Accordingly, when thesubstrate (wafer) 101 on which a plurality of semiconductor devices areformed is diced along the scribe region 103 so as to obtain theindividual semiconductor devices as chips, it is possible to preventmechanical impact or stress on the scribe region 103 during the dicingfrom propagating into the chip region 102.

In the seal ring structure shown in FIG. 2A, the cap layer 125 of, forexample, Al on the third seal via 124 formed on the uppermost interlayerdielectric film (i.e., fourth interlayer dielectric film 108) is formedin an opening provided in part of the protection film (passivation film109) on the third seal via 124, i.e., is formed in a trench provided inthe passivation film 109 to completely surround an interconnect layerand others formed in the chip region 102. Specifically, the cap layer125 connected to the top of the seal ring 104 is formed to protrude fromthe surface of the passivation film 109. Accordingly, the passivationfilm 109 partially opens to be discontinuous.

In this embodiment, part of the passivation film 109 located in the chipregion 102 and part of the passivation film 109 located outside the sealring region (including the scribe region 103) are discontinuous, so thatmechanical impact on the passivation film 109 near the scribe region 103during dicing is less likely to propagate into films such as thepassivation film 109 deposited in the chip region 102. That is, thepassivation film 109 is partially discontinuous in the chip region 102near the boundary between the chip region 102 and the scribe region 103,so that it is possible to prevent impact during dicing of the wafer fromreaching the chip region 102.

Accordingly, it is possible to prevent the phenomenon that impact duringdicing causes cracks or the like in part of the passivation film 109located in the scribe region 103 to make the passivation film 109 andothers peel off in the chip region 102. This avoids occurrence of cracksin the chip region 102. As a result, it is possible to prevent acontaminant such as moisture or mobile ions from entering the chip fromthe chip surface, thus enhancing the reliability of semiconductordevices.

In addition, the cap layer 125 is buried in the opening of thepassivation film 109 on the seal ring 104 so that the cap layer 125 andthe body of the seal ring 104 are continuous. Accordingly, unlike a casewhere the cap layer 125 is not provided, it is possible to preventmoisture or an impurity which has entered from the scribe region 103during dicing from penetrating into the chip region 102 via theperipheral part of the chip region 102, i.e., the opening of thepassivation film 109 near the scribe region 103.

In the seal ring structure of this embodiment shown in FIG. 2A, the sealring 104 is preferably narrow in part (specifically, the seal vias 121,123 and 124). Specifically, the aspect ratio (the ratio of the height tothe width) of this part is preferably one or more. In particular, theaspect ratio of a seal via formed without “junctions” through aninterlayer dielectric film in which a dual damascene interconnect isformed is preferably three or more. Alternatively, in a case where sealvias (e.g., the seal vias 123 and 124) are respectively formed throughtwo or more successive interlayer dielectric films, the aspect ratio ofthe structure of these stacked seal vias is preferably three or more. Inthis manner, if seal vias are used as conductors which are components ofthe seal ring 104, a margin for disposing the seal ring can be adjustedto some degree in accordance with an interconnect layout in interlayerdielectric films by utilizing the fact that the widths of vias aresmaller than those of interconnects. That is, in an interlayerdielectric film in which a wide range of the chip region 102 needs to beused to dispose an interconnect layer and others, a seal via ispreferably used as a component of the seal ring 104.

On the other hand, if the space for forming a seal ring therein in atarget interlayer dielectric film has a margin in consideration of aninterconnect layout of the chip region 102 and others, a sealinterconnect having substantially the same width as an interconnect canbe used. That is, a seal ring is formed by using a mask provided with aseal interconnect pattern having substantially the same width as aninterconnect pattern.

As described above, in this embodiment, the width of each component of aseal ring is selected for each dielectric film under consideration of aninterconnect layout of the chip region 102. Accordingly, the width(thickness) of each dielectric film for the seal ring is controlled asnecessary.

In this embodiment, instead of the seal ring structure shown in FIG. 2A,i.e., a seal ring structure in which at least two seal vias arecontinuously stacked, a seal ring 104 in which seal vias and sealinterconnects are alternately stacked in the same manner as in the sealring structure shown in FIG. 2B, i.e., an interconnect structure inwhich vias and interconnects are alternately stacked in the chip region102 where an element and others are formed, may be used.

Hereinafter, the seal ring structure shown in FIG. 2B will be describedspecifically. In FIG. 2B, components already shown in FIG. 2A aredenoted by the same reference numerals, and thus the description thereofwill be omitted.

As shown in FIG. 2B, the seal ring 104 is formed simultaneously with theformation of an interconnect structure in the chip region 102.Specifically, a first seal via 121 is formed through a first interlayerdielectric film 105 on a conductive layer 120. A first seal interconnect122 is formed through a second interlayer dielectric film 106 on thefirst interlayer dielectric film 105 to be connected to the first sealvia 121. In a third interlayer dielectric film 107 deposited on thesecond interlayer dielectric film 106, an interconnect (seal portion)with a dual damascene structure in which a second seal via 126 connectedto the first seal interconnect 122 and a second seal interconnect 127connected to the second seal via 126 are integrated is formed. In afourth interlayer dielectric film 108 on the third interlayer dielectricfilm 107, a seal portion with a dual damascene structure in which athird seal via 128 connected to the second seal interconnect 127 and athird seal interconnect 129 connected to the third seal via 128 areintegrated is formed. A passivation film 109 formed on the fourthinterlayer dielectric film 108 has an opening on top of the third sealinterconnect 129. A cap layer 125 connected to the third sealinterconnect 129 is formed in this opening.

In this manner, the semiconductor device of this embodiment shown inFIG. 2B includes the seal ring 104 with a structure similar to that ofan interconnect structure formed in the chip region 102, so that theseal ring 104 and the interconnect are formed by the same process.

In addition, in the semiconductor device of this embodiment shown inFIG. 2B, an interconnect structure, e.g., the second via 113 and thesecond interconnect 114, and components of the seal ring 104, e.g., thesecond seal via 126 and the second seal interconnect 127, are formed bythe same dual damascene process. Accordingly, a concave portion forforming the second seal via 126 and a trench for forming the second sealinterconnect 127 are integrated, so that the concave portion and thetrench are filled with a conductive film at the same time. As a result,no “junction” is present between the second seal via 126 and the secondseal interconnect 127. Specifically, if an interconnect structure and aseal ring 104 are formed by a dual damascene process in the manner as inthis embodiment, the number of “junctions” in the seal ring 104 isreduced, thereby forming the seal ring 104 capable of preventingmoisture or an impurity from entering the chip region 102 from theoutside of the scribe region 103 and others. As a result, the moistureresistance of semiconductor chips (semiconductor devices) is enhancedand the semiconductor chips are manufactured with high yield.

The seal ring structure shown in FIG. 2B is formed using photo masks inwhich a mask pattern for forming an interconnect structure in the chipregion 102 and a mask pattern for forming a seal ring coincide with eachother with respect to the same interlayer dielectric film. For example,when an interconnect with a dual damascene structure in which a via(plug) and an interconnect are integrated is formed in the interlayerdielectric film 107 in the chip region 102, a dual damascene process isalso employed to form a component of the seal ring 104 in thisinterlayer dielectric film 107. Specifically, the component of the sealring 104 formed in the interlayer dielectric film 107 is constituted bythe second seal via 126 having substantially the same width as thesecond via 113 and the second seal interconnect 127 having substantiallythe same width as the second interconnect 114. In the interlayerdielectric film 107, the multilayer structure made of the second sealvia 126 and the second seal interconnect 127 is formed to verticallypenetrate the interlayer dielectric film 107 and completely surround(without an interruption) the chip region 102.

The seal ring 104 shown in FIG. 2B is formed by alternately stackingseal interconnects and seal vias and the width of a seal interconnect islarger than that of the associated seal via. Accordingly, the strengthof the seal ring is enhanced, as compared to a seal ring formed bystacking only seal vias or stacking seal vias for the most part.

The method for fabricating a semiconductor device with the structureshown in FIG. 2B is different from that for fabricating a semiconductordevice with the structure shown in FIG. 2A only in mask patterns forforming the seal ring in respective photo masks. Specifically, informing the seal ring 104 shown in FIG. 2A, for example, mask patternsfor forming the seal ring in respective masks which have beenpredetermined so as to form the third seal via 124 on the second sealvia 123 are altered in the formation of the seal ring 104 shown in FIG.2B. More specifically, mask patterns for forming a seal ring inrespective masks are defined such that the second seal interconnect 127is formed on the second seal via 126 and the third seal interconnect 129is formed on the third seal via 128, i.e., such that seal vias and sealinterconnects are alternately formed.

Hereinafter, the seal ring structure shown in FIG. 3A, i.e., a seal ring104 in which a seal via is divided into at least two branches in aninterlayer dielectric film, will be described specifically. In FIG. 3A,components already shown in FIG. 2A are denoted by the same referencenumerals, and thus the description thereof will be omitted.

The seal ring structure shown in FIG. 3A is different from that shown inFIG. 2A in the following aspects. First, instead of the first seal via121, seal vias 121 a and 121 b connected to the conductive layer 120 areprovided through the first interlayer dielectric film 105. Second,instead of the second seal via 123, seal vias 123 a and 123 b connectedto the first seal interconnect 122 are provided through the thirdinterlayer dielectric film 107. Third, instead of the third seal via124, seal vias 124 a and 124 b connected to the respective seal vias 123a and 123 b are provided through the fourth interlayer dielectric film108. The tops of the respective seal vias 121 a and 121 b are connectedto the first seal interconnect 122, and the tops of the respective sealvias 124 a and 124 b are connected to the cap layer 125.

That is, the method for fabricating a semiconductor device with thestructure shown in FIG. 3A is different from that for fabricating asemiconductor device with the structure shown in FIG. 2A in that maskpatterns for forming two seal vias are provided in photo masks for usein etching of an interlayer dielectric film, and a conductive film isburied in a pair of parallel trench concave portions formed by usingthese mask patterns.

In addition to the advantages obtained by the seal ring structure shownin FIG. 2A, the seal ring structure shown in FIG. 3A has the followingadvantages. Since a seal via is narrower than a seal interconnect, thestrength of the seal via is relatively lower than that of the sealinterconnect. On the other hand, if a seal via divided into at least twobranches is used instead of a single seal via as a component of a sealring as in the seal ring structure shown in FIG. 3A, the seal ringpartially has a multiplex structure (i.e., a structure in which the chipregion 102 is surrounded by multiple seal ring branches) in aninterlayer dielectric film in which the seal via is divided into thebranches. Accordingly, as compared to a seal ring which is not dividedinto branches in an interlayer dielectric film (i.e., which has a singlestructure), the strength of the seal ring with the multiplex structureshown in FIG. 3A is enhanced. It should be noted that in terms ofprocessing, the seal ring structure shown in FIG. 2A is more easilyimplemented than the seal ring structure shown in FIG. 3A.

With the seal ring structure shown in FIG. 3A, even if the seal ring 104is damaged in part by impact involved in dicing of a wafer (substrate101) into chips along the scribe region 103, it is possible to preventthe chip region 102 inside the scribe region 103 from being affected bythe impact as long as the seal ring 104 in this damaged part has amultiplex structure including two or more branches. Specifically, it ispossible to suppress entering of moisture from the scribe region 103into the chip region 102 or propagation of the impact during dicing ofthe wafer along the scribe region 103 into the chip region 102.

The seal ring 104 shown in FIG. 3A has a structure in which a seal viais divided into two branches connected to one seal interconnect.Alternatively, a seal via may be divided into three or more branchesconnected to one seal interconnect. In the seal ring 104 shown in FIG.3A, each of the seal vias is divided into a plurality of branches in afilm. Alternatively, the seal via may be selectively divided intobranches in each film, depending on a margin on a layout necessary foran interconnect layer formed in the chip region 102, or the strength ofa film (interlayer dielectric film), for example.

In this embodiment, an interconnect structure is formed in four stackedinterlayer dielectric films. However, the number of interlayerdielectric films is not limited to four and may of course be smaller orgreater than four depending on the structure of a chip.

In this embodiment, Cu is used as a conductive material constituting theseal ring 104. However, the present invention is not limited to this,and the seal ring 104 may be made of at least one of W, Al and Cu. Then,the seal ring 104 is formed out of the same material as interconnectsand vias formed in the chip region 102 of a semiconductor device.

In this embodiment, the conductive material constituting the cap layer125 is not specifically limited. However, use of Al as the conductivematerial ensures prevention of erosion of the seal ring 104 (especiallya seal ring made of Cu.)

In this embodiment, in a case where a plurality of seal vias arecontinuously stacked as in the seal ring structure shown in FIG. 2A or3A, for example, the contact surface of an upper seal via or a lowerseal via is preferably larger than that of the other seal via. Then, thecontact margin is enhanced.

Embodiment 2

Hereinafter, a semiconductor device and a method for fabricating thedevice according to a second embodiment of the present invention will bedescribed with reference to drawings.

FIG. 7 is a plan view showing part of a wafer on which a semiconductordevice of the second embodiment (i.e., a semiconductor device in which achip region is surrounded by two seal rings) is provided. Hereinafter, aseal ring structure including two or more seal rings surrounding a chipregion will be also referred to as a multi-seal ring structure.

As shown in FIG. 7, on a wafer 201 to be a semiconductor substrate,typically a silicon substrate, for example, a plurality of chip regions202 to be semiconductor devices, are provided. In each of the chipregions 202, an IC made of a plurality of elements and provided with agiven function is formed. The chip regions 202 are defined by a scriberegion 203 having a lattice pattern.

A semiconductor device (i.e., a semiconductor chip) includes: an IC(located in the chip region 202) made of a plurality of elements andprovided with a given function; and seal rings 204 a and 204 b providedin a peripheral part of the chip region 202 to surround the chip region202. In this embodiment, a multi-seal ring structure including two sealrings is used. Alternatively, a multi-seal ring including three, four ormore seal rings may be used depending on a margin on a layout.

After formation of chips has been completed, the wafer 201 on which aplurality of semiconductor devices each having its chip region 202surrounded by the multi-seal ring structure 204 are formed is dicedalong the scribe region 203, thereby separating the semiconductordevices from each other.

In this embodiment, the seal ring structure 204 having at least two sealrings is formed in the chip region 202 near the scribe region 203.Accordingly, even if one of the seal rings (e.g., the outermost sealring) is damaged during dicing of the wafer 201, damage to an element,an active region and others in the chip region 202 is prevented by theother inner seal ring(s). This eliminates degradation of performance ofa semiconductor chip caused by occurrence of a crack in the chip region202, including an element, an active region and others, during dicing ofthe wafer 201 into chips.

FIGS. 8A and 8B show variations of the cross-sectional structure takenalong the line B-B′ in FIG. 7 (the cross-sectional structure of an endof a semiconductor device including a seal ring portion located in aperipheral part of the chip region 202.)

As shown in FIGS. 7, 8A and 8B, a semiconductor device before dicingincludes to the chip regions 202 and the scribe region 203, and the sealrings 204 a and 204 b are formed in the chip region 202 near theboundary between the chip region 202 and the scribe region 203.

Now, features of the respective structures shown in FIGS. 8A and 8B willbe described specifically.

First, the structure shown in FIG. 8A has a feature in which seal viasconstituting each of the seal rings 204 a and 204 b are continuouslyformed through at least two successive films.

Next, the structure shown in FIG. 8B has a feature in which seal viasconstituting each of the seal rings 204 a and 204 b are continuouslyformed through at least two successive films, two or more adjacent sealvias are formed in the same interlayer dielectric film, and these two ormore adjacent seal vias are connected to one seal interconnect formed ina dielectric film located on top or bottom of the film in which the sealvias are formed. That is, each seal via constituting the seal ringstructure 204 shown in FIG. 8B is divided into two or more branches inthe same interlayer dielectric film.

On the other hand, the structures shown in FIGS. 8A and 8B have a commonfeature in which the seal ring structure 204 includes at least two sealrings and seal ring caps (cap layers 225 a and 226 b) are provided atthe tops of the respective seal rings 204 a and 204 b.

Hereinafter, a method for fabricating a semiconductor device having thestructure shown in FIG. 8A will be described with reference to FIGS. 9Athrough 9D and 10A through 10C.

First, as shown in FIG. 9A, an active layer 210 constituting an elementsuch as a transistor is formed in a wafer 201 (hereinafter, referred toas a substrate 201) in a chip region 202. At the same time, two adjacentconductive layers 220 a and 220 b are formed in to the substrate 201 ina peripheral part of the chip region 202 (a seal ring region near ascribe region 203.) The conductive layers 220 a and 220 b have similarconfiguration as that of the active layer 210.

Then, a first interlayer dielectric film 205 is deposited on thesubstrate 201. Subsequently, through a lithography process and a dryetching process, a via hole 205 a for forming a first via 211 (see FIG.9B) is formed through the first interlayer dielectric film 205 in thechip region 202 and, at the same time, trench concave portions 205 b and205 c for forming first seal vias 221 a and 221 b (see FIG. 9B) on therespective adjacent conductive layers 220 a and 220 b are formed throughthe first interlayer dielectric film 205 in the seal ring region. Theseal vias are components of seal rings and are formed by filling thetrench concave portions with a conductive material. Specifically, eachseal via has a line structure having substantially the same width as avia in the chip region.

In this embodiment, the aspect ratio of a seal via (i.e., the ratio ofthe depth to the width in a concave portion in which the seal via isburied) is preferably one or more. In particular, in the case where sealvias are formed simultaneously with an interconnect layer as in thisembodiment, the aspect ratio of each seal via is preferably set at threeor more in accordance with the degree of miniaturization ofinterconnects.

In this embodiment, the trench concave portions 205 b and 205 c forforming the first seal vias 221 a and 221 b and the via hole 205 a areformed at the same time in the first interlayer dielectric film 205 inthe chip region 202. Alternatively, the via hole 205 a and the trenchconcave portions 205 b and 205 c may of course be formed individually.

Next, as shown in FIG. 9B, the via hole 205 a and the trench concaveportions 205 b and 205 c formed through the first interlayer dielectricfilm 205 are filled with a conductive film made of, for example, W by,for example, a CVD process. Then, an unnecessary part of the conductivefilm extending off the via hole 205 a and the trench concave portions to205 b and 205 c is removed by, for example, a CMP process, therebyforming a first via 211 connected to the active layer 210 and adjacentfirst seal vias 221 a and 221 b connected to the respective conductivelayers 220 a and 220 b.

Thereafter, a second interlayer dielectric film 206 is deposited on thefirst interlayer dielectric film 205. Then, through a lithographyprocess and a dry etching process, an interconnect trench 206 a forforming a first interconnect 212 (see FIG. 9C) is formed through thesecond interlayer dielectric film 206 in the chip region 202, and at thesame time, interconnect trenches 206 b and 206 c for forming adjacentfirst seal interconnects 222 a and 222 b (see FIG. 9C) are formedthrough the second interlayer dielectric film 206 in the seal ringregion.

Then, as shown in FIG. 9C, the interconnect trenches 206 a, 206 b and206 c formed through the second interlayer dielectric film 206 arefilled with a conductive film of, for example, Cu by, for example, anelectroplating process. Thereafter, part of the conductive filmextending off the interconnect trenches 206 a, 206 b and 206 c isremoved by, for example, a CMP process, thereby forming a firstinterconnect 212 connected to the first via 211 and adjacent first sealinterconnects 222 a and 222 b connected to the respective first sealvias 221 a and 221 b.

Subsequently, a third interlayer dielectric film 207 is deposited on thesecond interlayer dielectric film 206, and then a via hole 207 a forforming a second via 213 (see FIG. 10A) is formed through the thirdinterlayer dielectric film 207 in the chip region 202. At the same time,trench concave portions 207 b and 207 c for forming adjacent second sealvias 223 a and 223 b (see FIG. 10A) are formed through the thirdinterlayer dielectric film 207 in the seal ring region.

Then, as shown in FIG. 9D, a resist film 230 for forming an interconnecttrench in which a second interconnect 214 (see FIG. 10A) is to be buriedis formed on the third to interlayer dielectric film 207 using alithography process. This resist film 230 has an opening on aninterconnect region including the via hole 207 a. The resist film 230 isalso buried in the trench concave portions 207 b and 207 c.

Thereafter, through a dry etching process using the resist film 230 as amask, an interconnect trench connected to the via hole 207 a and usedfor forming the second interconnect 214 is formed in an upper part ofthe third interlayer dielectric film 207 in the chip region 202. Then,the remaining resist film 230 is removed by ashing. Thereafter, aconductive film made of, for example, Cu is buried in the via hole 207a, the interconnect trench integrated with the via hole 207 a to form aconcave portion with a dual damascene structure, and the trench concaveportions 207 b and 207 c formed in the third interlayer dielectric film207 by the previous process steps. Then, part of the conductive filmextending off the interconnect trench and the trench concave portions207 b and 207 c (i.e., part of the conductive film located above thethird interlayer dielectric film 207) is removed by, for example, a CMPprocess. In this manner, as shown in FIG. 10A, a second via 213connected to the first interconnect 212 and a second interconnect 214connected to the second via 213 are formed (i.e., a dual damasceneinterconnect constituted by the second via 213 and the secondinterconnect 214 is formed) in the third interlayer dielectric film 207in the chip region 202. At the same time, two adjacent second seal vias223 a and 223 b connected to the respective first seal interconnects 222a and 222 b are formed through the third interlayer dielectric film 207in the seal ring region. The process of simultaneously forming a via andan interconnect by burying a conductive film in a concave portion asdescribed above is generally called a dual damascene process.

If the second via 213 and the second interconnect 214 are formed by asingle damascene process, different conductive films are buried in thevia hole 207 a for forming the second via 213 and the interconnecttrench for forming the second interconnect 214, to respectively.Therefore, since this interconnect structure and the second seal vias223 a and 223 b are formed by the same process, two burying processes ofthe conductive films are also performed on the trench concave portions207 b and 207 c. In this case, “junctions” created by these two buryingprocesses occur inside the second seal vias 223 a and 223 b.

However, in this embodiment, the second seal vias 223 a and 223 b areformed by burying a conductive film only once in the process for formingan interconnect with a dual damascene structure, so that no junction iscreated between conductive films in the seal vias.

In the case where an interconnect with a dual damascene structure isformed in an interlayer dielectric film in the chip region 202 and sealvias constituting the seal ring structure 204 are formed in thisinterlayer dielectric film as in this embodiment, each of the resultantseal vias has an aspect ratio of three or more. Accordingly, the numberof junctions between components of the seal ring structure 204 isreduced, so that a seal ring structure which further ensures preventionof contamination of the chip region 202 from the outside.

Subsequently, as shown in FIG. 10B, a fourth interlayer dielectric film208 is deposited on the third interlayer dielectric film 207, and thenan interconnect structure with a dual damascene and a seal ring areformed in the fourth interlayer dielectric film 208 by a dual damasceneprocess, in the same manner as in the process steps shown in FIGS. 9Cthrough 10A.

Specifically, as shown in FIG. 10B, through a lithography process and adry etching process, a via hole for forming a third via 215 is formedthrough the fourth interlayer dielectric film 208 in the chip region 202and, at the same time, two trench concave portions for forming adjacentthird seal vias 224 a and 224 b are formed through the fourth interlayerdielectric film 208 in the seal ring region. Thereafter, a resist film(not shown) for forming an interconnect trench in which a thirdinterconnect 216 is to be buried is formed on the fourth interlayerdielectric film 208 using a lithography process. This resist film has anopening on the interconnect region including the via hole. The resistfilm is also buried in the trench concave portions. Then, through a dryetching process using the resist film as a mask, an interconnect trenchconnected to the via hole and used for forming the third interconnect216 is formed in an upper part of the fourth interlayer dielectric film208 in the chip region 202. Then, the remaining resist film is removedby ashing. In this manner, a concave portion (i.e., the via hole and theinterconnect trench) for forming a dual damascene interconnect and twotrench concave portions for forming the third seal vias 224 a and 224 bare formed in the fourth interlayer dielectric film 208.

Subsequently, as shown in FIG. 10B, a conductive film made of, forexample, Cu is buried in a concave portion with the dual damascenestructure in which the via hole for forming the third via 215 and theinterconnect trench for forming the third interconnect 216 areintegrated and also buried in the trench concave portions for formingthe respective third seal vias 224 a and 224 b, in the fourth interlayerdielectric film 208. Then, part of the conductive film extending off theinterconnect trench and the trench concave portions (i.e., part of theconductive film located above the fourth interlayer dielectric film 208)is removed by, for example, a CMP process. In this manner, a third via215 connected to the second interconnect 214 and a third interconnect216 connected to the third via 215 are formed (i.e., a dual damasceneinterconnect constituted by the third via 215 and the third interconnect216 is formed) in the fourth interlayer dielectric film 208 in the chipregion 202. At the same time, third seal vias 224 a and 224 b connectedto the respective second seal vias 223 a and 223 b are formed throughthe fourth interlayer dielectric film 208 in the seal ring region.

Thereafter, as shown in FIG. 10B, on the fourth interlayer dielectricfilm 208, which is the uppermost interconnect layer, a passivation film209 serving as a protection film of this uppermost interconnect layer isdeposited. Then, parts of the passivation film 209 on the thirdinterconnect 216 and the adjacent third seal vias 224 a and 224 b areremoved by a lithography process and a dry etching process, therebyforming openings. In this manner, the upper surfaces of the respectivethird interconnect 216 and the third seal vias 224 a and 224 b areexposed.

Thereafter, as shown in FIG. 10C, an Al film, for example, is depositedby, for example, a spattering process over the entire surface of thepassivation film 209 including the openings on the third interconnect216 and the third seal vias 224 a and 224 b. Then, this Al film ispatterned into a predetermined shape by a lithography process and a dryetching process. Specifically, an unnecessary part of the Al film on theregion except for the openings and their neighboring regions is removed.In this manner, a pad electrode 217 connected to the third interconnect216 is formed in the opening of the passivation film 209 on the thirdinterconnect 216, and cap layers 225 a and 225 b connected to therespective third seal vias 224 a and 224 b, i.e., the respective sealrings 204 a and 204 b, are formed in the openings of the passivationfilm 209 on the respective third seal vias 224 a and 224 b.

In this manner, an interconnect structure and a bonding pad (padelectrode 217) for connecting the interconnect structure to an externalelectrode are formed in the chip region 202, whereas the seal rings 204a and 204 b and the cap layers 225 a and 225 b, which are connected tothe respective seal rings 204 a and 204 b through the protection film(passivation film 209) deposited on the seal rings 204 a and 204 b, areformed in the seal ring region, i.e., in the peripheral part of the chipregion 202 (near the boundary between the chip region 202 and the scriberegion 203.)

As described above, in this embodiment, an interconnect structure isformed by using a dual damascene process with which a conductive film isburied in a hole for forming a via and a trench for forming aninterconnect at the same time. Seal vias constituting seal rings arealso formed by the process for forming the interconnect structure.Specifically, an interconnect trench with a dual damascene structure inwhich a concave portion for forming a via and an interconnect trench forforming an interconnect are integrated is filled simultaneously withconcave portions for forming seal vias at the same time. Accordingly,the concave portions for forming seal vias having sufficient heights,i.e., concave portions for forming seal vias whose aspect ratio of thedepth to the width, for example, is one or more (preferably three ormore), are filled by single burying process.

Therefore, in this embodiment, the resultant seal ring structure has asmaller number of “junctions” originating from burying of conductivefilms, as compared to the case of forming an interconnect by a singledamascene process. Specifically, a merit of a small number of buryingprocesses of conductive films is that the number of interfaces betweenconductive films constituting a seal ring is reduced. That is,discontinuous portions due to poor burying of conductive films are lesslikely to occur between components of a seal ring, resulting in that theresultant seal ring structure exhibits higher reliability than a sealring structure obtained through a large number of burying processes(i.e., a seal ring structure formed by a single damascene process.)

In this embodiment, the cap layers 225 a and 225 b connected to the topsof the respective seal rings 204 a and 204 b are formed simultaneouslywith the formation of a pad (pad electrode 217) for supplying power fromthe outside to an IC and others in the chip region 202 or for taking asignal from the IC and others to the outside. This allows the seal rings204 a and 204 b including the cap layers 225 a and 225 b at theirrespective tops to be formed without an additional process for formingthe cap layers.

In addition to the advantages obtained by the first embodiment, thesecond embodiment has the following advantages.

Specifically, in the second embodiment, the seal ring structure 204including two seal rings completely surrounding the chip region 202 isformed in the peripheral part of the chip region 202. Accordingly, whenthe semiconductor wafer (substrate) 201 is diced along the scribe region203 so as to obtain individual completed semiconductor chips(semiconductor devices), prevention of propagation, into the chip region202, of mechanical impact caused by contact of a dicing blade with thescribe line (scribe region) 203 during dicing or prevention of damage tothe chip region 202 due to the propagation is further ensured.

In addition, in the second embodiment, the two cap layers 225 a and 225b are formed at the tops of the respective seal rings 204 a and 204 b,so that the following advantages are obtained.

FIG. 11A is a plan view showing a structure of the semiconductor device(semiconductor chip) shown in FIG. 10C (or FIG. 8A) when viewed fromabove (from above the passivation film (protection film) 209 formed onthe uppermost interconnect layer). FIG. 11A shows one of semiconductorchips 201A formed on the wafer (substrate) 201.

As shown in FIG. 11A, the scribe region 203 is provided to surround thechip region 202, and the two seal rings 204 a and 204 b (not shownbecause these rings are formed under the cap layers 225 a and 225 b) areformed in the chip region 202 near the boundary between the chip region202 and the scribe region 203. The cap layers 225 a and 225 b formed atthe tops of the respective seal rings 204 a and 204 b are provided inthe openings (formed by partly removing the passivation film 209) of thepassivation film 209 completely surrounding the chip region 202.Accordingly, part of the passivation film 209 in the chip region 202 andpart of the passivation film 209 in the scribe region 203 are separatedfrom each other by these two cap layers 225 a and 225 b. That is,connection between the scribe region 203 and the chip region 202 via thepassivation film 209 is not established, so that impact on part of thepassivation film 209 in the scribe region 203 during dicing hardlypropagates through the passivation film 209 into the chip region 202.

FIG. 11B is a cross-sectional view showing the surface of a chip takenalong the line C-C′ in FIG. 11A.

As shown in FIG. 11B, the two cap layers 225 a and 225 b are formedthrough the passivation film 209 in the peripheral part of the chipregion 202. Accordingly, it is possible to prevent impact, stress or thelike on the passivation film 209 in the scribe region 203 caused bycontact with a dicing blade during dicing from affecting a circuit, aninterconnect structure and others inside the chip region 202.

Hereinafter, the seal ring structure shown in FIG. 8B, i.e., a structurein which each of the seal vias constituting the seal rings 204 a and 204b is divided into at least two branches in an interlayer dielectricfilm, will be described specifically. In FIG. 8B, components also shownin FIG. 8A are denoted by the same reference numerals, and thus thedescription thereof will be omitted.

The seal ring structure shown in FIG. 8B is different from that of theseal ring structure shown in FIG. 8A in that each of the seal viasconstituting the seal rings 204 a and 204 b is divided into at least twoin an interlayer dielectric film.

Specifically, for the inner seal ring (first seal ring) 204 a in thedouble structure including the first seal ring 204 a and the outer sealring (second seal ring) 204 b, seal vias 221 a 1 and 221 a 2 connectedto the conductive layer 220 a are provided instead of the first seal via221 a in the first interlayer dielectric film 205, seal vias 223 a 1 and223 a 2 connected to the first seal interconnect 222 a are providedinstead of the second seal via 223 a in the third interlayer dielectricfilm 207, and seal vias 224 a 1 and 224 a 2 connected to the respectiveseal vias 223 a 1 and 223 a 2 are provided instead of the third seal via224 a in the fourth interlayer dielectric film 208. The tops of therespective seal vias 221 a 1 and 221 a 2 are connected to the first sealinterconnect 222 a, and the tops of the respective seal vias 224 a 1 and224 a 2 are connected to the cap layer (first cap layer) 225 a.

For the second seal ring 204 b located adjacent to the first seal ring204 a and outside the first seal ring 204 a, seal vias 221 b 1 and 221 b2 connected to the conductive layer 220 b are provided instead of thefirst seal via 221 b in the first interlayer dielectric film 205, sealvias 223 b 1 and 223 b 2 connected to the first seal interconnect 222 bare provided instead of the second seal via 223 b in the thirdinterlayer dielectric film 207, and seal vias 224 b 1 and 224 b 2connected to the respective seal vias 223 b 1 and 223 b 2 are providedinstead of the third seal via 224 b in the fourth interlayer dielectricfilm 208. The tops of the respective seal vias 221 b 1 and 221 b 2 areconnected to the first seal interconnect 222 b, and the tops of therespective seal vias 224 b 1 and 224 b 2 are connected to the cap layer(second cap layer) 225 b.

As described above, the seal rings 204 a and 204 b shown in FIG. 8B havea structure in which a plurality of branches of a seal via (or amultilayer structure of such branches) are bundled by at least one sealinterconnect. Accordingly, even if the width (thickness) of each sealvia is small, the bundle of the branches provides the seal rings withhigh strength as a whole. Therefore, even if mechanical impact or stressis applied to the scribe region 203 during dicing, it is possible toprevent the seal ring 204 a or 204 b from being damaged or preventdamage to part of the seal ring 204 a or 204 b (i.e., one of thebranches of seal vias) from affecting the chip region 202.

In the seal ring structure shown in FIG. 8B, each of the seal viasconstituting the seal rings 204 a and 204 b is selectively divided intotwo, three, four or more in an interlayer dielectric film, thusenhancing protection of the chip region 202. That is, prevention ofpropagation of impact or stress during dicing into the chip region 202is further ensured.

In the seal ring structure shown in FIG. 8B, as in the seal ringstructure shown in FIG. 8A, even if the outer second seal ring 204 b isdamaged, it is still possible to prevent a contaminant such as moistureor mobile ions from entering the chip region 202 and thereby degradationof the reliability of a semiconductor device is avoided, as long as thefirst seal ring 204 a, which is electrically insulated from the secondseal ring 204 b, is not damaged and has its shape maintained.

In the seal ring structure shown in FIG. 8B, a seal via is divided intotwo branches connected to one seal interconnect. Alternatively, the sealvia may be divided into three or more branches connected to one sealinterconnect. That is, the number of branches of a seal via may beappropriately selected in accordance with a margin on the layout of thechip region 202 or the strength of the film (interlayer dielectricfilm.)

In the seal rings 204 a and 204 b shown in FIGS. 8A and 8B, instead ofthe structure in which two or more seal vias are continuously stacked, astructure in which seal vias and seal interconnects are alternatelystacked, e.g., an interconnect structure in which vias and interconnectsare alternately stacked in the chip region 202 including an element andothers are formed, may be used. In such a case, the same advantages asthose obtained in this embodiment are obtained. It should be noted thata seal ring using a seal interconnect has a larger width than that usinga seal via. Therefore, it is preferable to determine whether a sealinterconnect is used or not in consideration of layouts of respectiveinterconnect layers.

In this embodiment, an interconnect structure is formed in foursuccessive interlayer dielectric films. However, the number of suchinterlayer dielectric films is not limited to four and may of course besmaller or larger than four, depending on the structure of the chip.

In this embodiment, Cu is used as a conductive material constituting theseal rings 204 a and 204 b. However, the present invention is notlimited to this, and the seal rings 204 a and 204 b may be made of atleast one of W, Al and Cu. Then, the seal rings 204 a and 204 b areformed out of the same material as that constituting interconnects andvias formed in the chip region 202 of a semiconductor device.

In addition, in this embodiment, the conductive material constitutingthe cap layers 225 a and 225 b is not specifically limited. However, ifthe conductive material is Al, prevention of erosion of the seal rings204 a and 204 b (especially seal rings made of Cu) is ensured.

Moreover, in this embodiment, if a plurality of seal vias arecontinuously stacked as in the seal ring structures shown in FIGS. 8Aand 8B, for example, the contact surface of an upper seal via or a lowerseal via is preferably larger than that of the other seal via. Then, thecontact margin is increased.

Modified Example 1 of Embodiment 2

Hereinafter, a semiconductor device and a method for fabricating thedevice according to a first modified example of the second embodimentwill be described with reference to drawings.

FIG. 12A is a cross-sectional view (a view showing the cross-sectionalstructure taken along the line B-B′ in FIG. 7) of a semiconductor deviceaccording to this modified example.

The seal ring structure of this modified example shown in FIG. 12A isdifferent from that of the second embodiment shown in FIG. 8A in thatthe cap layer (first cap layer) 225 a is not provided at the top of theinner seal ring (first seal ring) 204 a. In other words, the passivationfilm 209 has no opening on the first seal ring 204 a.

Specifically, as shown in FIG. 12A, the semiconductor device of thismodified example has a double seal ring structure as in the secondembodiment. An outer second seal ring 204 b in this structure includes acap layer (second cap layer) 225 b at its top as in the seal ringstructure of the first embodiment shown in FIG. 2A, whereas an innerfirst seal ring 204 a does not include a cap layer at its top.

As in the seal ring structure of the second embodiment shown in FIG. 8A,the first and second seal rings 204 a and 204 b of this modified exampleare formed in a multilayer structure made of a plurality of interlayerdielectric films 205 through 209. More specifically, first seal vias 221a and 221 b are formed on respective conductive layers 220 a and 220 bprovided in a substrate 201, and first seal interconnects 222 a and 222b are formed on the respective first seal vias 221 a and 221 b. Secondseal vias 223 a and 223 b are formed on the respective first sealinterconnects 222 a and 222 b, and third seal vias 224 a and 224 b areformed on the respective second seal vias 223 a and 223 b. A passivationfilm 209 is formed on the third seal via 224 a and has an opening on thethird seal via 224 b, which is located at the top of the outer secondseal ring 204 b. A cap layer 225 b connected to the third seal via 224 bis formed in the opening.

In this modified example, the two seal rings 204 a and 204 b are formedto completely surround the chip region 202. Accordingly, when thesemiconductor wafer (substrate) 201 is diced along a scribe region 203to obtain individual completed semiconductor chips (semiconductordevices), prevention of propagation, to the chip region 202, ofmechanical impact or stress caused by contact of a dicing blade with thescribe line (scribe region) 203 during dicing or prevention of damage tothe chip region 202 due to the propagation is further ensured.

In this modified example, the cap layer 225 b is formed at the top ofthe outer second seal ring 204 b and penetrates the passivation film209. Accordingly, part of the passivation film 209 in the chip region202 and part of the passivation film 209 in the scribe region 203 arecompletely separated from each other by the cap layer 225 b to bediscontinuous. As a result, it is possible to prevent impact on thescribe region 203 during dicing from propagating to the chip region 202.

Modified Example 2 of Embodiment 2

Hereinafter, a semiconductor device and a method for fabricating thedevice according to a second modified example of the second embodimentwill be described with reference to drawings.

FIG. 12B is a cross-sectional view (a view showing the cross-sectionalstructure taken along the line B-B′ in FIG. 7) of a semiconductor deviceaccording to this modified example.

The seal ring structure of this modified example shown in FIG. 12B isdifferent from that of the second embodiment shown in FIG. 8B in thatthe cap layer (first cap layer) 225 a is not provided at the top of theinner seal ring (first seal ring) 204 a. In other words, the passivationfilm 209 has no opening on the first seal ring 204 a. Specifically, thesemiconductor device of this modified example has a double seal ringstructure as in the second embodiment. An outer second seal ring 204 bin the structure of this modified example includes a cap layer (secondcap layer) 225 b at its top as in the seal ring structure of the firstembodiment shown in FIG. 3A, whereas an inner first seal ring 204 a doesnot include a cap layer at its top.

The seal ring structure of this modified example shown in FIG. 12B isdifferent from that of the first modified example of the secondembodiment shown in FIG. 12A in that each seal via constituting the sealrings 204 a and 204 b has branches.

Specifically, each of first seal vias 221 a and 221 b in the firstinterlayer dielectric to film 205 is divided into two branches, i.e.,first seal vias 221 a 1 and 221 a 2 or first seal vias 221 b 1 and 221 b2, respectively. Likewise, each of second seal vias 223 a and 223 b inthe third interlayer dielectric film 207 is divided into two branches,i.e., second seal vias 223 a 1 and 223 a 2 or second seal vias 223 b 1and 223 b 2, respectively. Each of third seal vias 224 a and 224 b inthe fourth interlayer dielectric film 208 is divided into two branches,i.e., third seal vias 224 a 1 and 224 a 2 or third seal vias 224 b 1 and224 b 2, respectively. A passivation film 209 is formed over the thirdseal vias 224 a 1 and 224 a 2 whereas the passivation film 209 has anopening on the third seal vias 224 b 1 and 224 b 2, which are located atthe top of the outer second seal ring 204 b. A cap layer 225 b connectedto the third seal vias 224 b 1 and 224 b 2 is formed in the opening.

In addition to the advantages obtained in the first modified example ofthe second embodiment shown in FIG. 12A, the following advantage isobtained in this modified example. That is, since seal vias constitutingthe seal rings 204 a and 204 b have branches, the strength of the sealrings 204 a and 204 b is enhanced and the seal rings 204 a and 204 bprevent an impurity or moisture from entering the chip region 202 fromthe outside.

Modified Example 3 of Embodiment 2

Hereinafter, a semiconductor device and a method for fabricating thedevice according to a third modified example of the second embodimentwill be described with reference to drawings.

FIG. 13 is a cross-sectional view (a view showing the cross-sectionalstructure taken along the line B-B′ in FIG. 7) of a semiconductor deviceaccording to this modified example.

The semiconductor device of this modified example shown in FIG. 13 isdifferent from that of the second embodiment shown in FIG. 8B in that atransistor is provided in part of the substrate 201 in the chip region202 near the seal rings 204 a and 204 b. Specifically, a gate electrode233 is formed over an area of the substrate 201 surrounded by anisolation 231 with a gate insulating film 232 interposed therebetween.An insulating sidewall 234 is formed on side faces of the gate electrode233. An active layer 210 to be source/drain regions is defined in partsof the substrate 201 below the sides of the gate electrode 233.

The seal ring structure of this modified example shown in FIG. 13 isdifferent from that of the second embodiment shown in FIG. 8B in thateach of the first seal vias 221 a and 221 b in the first interlayerdielectric film 205 in which the transistor is formed is divided intotwo first seal vias 221 a 1 and 221 a 2 or two first seal vias 221 b 1an 221 b 2, respectively. As in the seal ring structure of the firstmodified example of the second embodiment shown in FIG. 12A, the caplayer (first cap layer) 225 a is not provided on an inner seal ring(first seal ring) 204 a. In other words, a passivation film 209 does nothave an opening on the first seal ring 204 a.

With recent reduction in chip size, the distance from a portion of awafer at which the wafer is diced (i.e., a scribe region) to thetransistor closest to this portion (hereinafter, referred to as anearest transistor) has decreased. Specifically, in a conventionaldevice in which no element is provided under a pad, the distance from aseal ring to the nearest transistor (corresponding to distance L in FIG.13) is approximately 100 μm. On the other hand, such a layout that anelement is provided under a pad has been employed in recent years, andthe distance L from a seal ring to the nearest transistor has beenreduced to approximately 10 μm accordingly. As a result, impact duringdicing easily propagates to the transistor so that the transistor isreadily damaged. On the other hand, since the transistor has aminiaturized structure including a thin gate oxide film and others, thetransistor is vulnerable to impact. Therefore, transistors need to haveprotection especially against damage during dicing.

In view of this, in this modified example, the “seal via structurehaving two or more branches” described above is employed to enhance thestrength of the seal ring structure of a transistor layer. Specifically,each of the first seal vias 221 a and 221 b constituting the seal rings204 a and 204 b is divided into two branches in the dielectric film asthe bottom layer on the substrate 201, i.e., the first interlayerdielectric film 205 as a transistor layer including the gate electrode233 and others, so that each of the branches, i.e., the seal vias 221 a1, 221 a 2, 221 b 1 and 221 b 2, serves as a bather against impact onthe bottom layer in the chip region 202. In this manner, damage to atransistor during dicing is prevented, thus enhancing the yield inmanufacturing semiconductor devices.

In this modified example, the “seal via structure having two or morebranches” is used in a layer in which a miniaturized transistor isprovided. Alternatively, the “seal via structure having two or morebranches” may be used in a miniaturized layer or a layer having aminiaturized structure.

Embodiment 3

Hereinafter, a semiconductor device and a method for fabricating thedevice according to a third embodiment of the present invention will bedescribed with reference to drawings. In this embodiment, variations ofthe first and second embodiments will be described.

FIG. 14A is a view schematically showing a cross-sectional structure ofthe conventional semiconductor device shown in FIG. 19. FIG. 14A showsperipheral parts of two chip regions 2 sandwiching the scribe region 3.In FIG. 14A, some components are not shown and components also shown inFIG. 19 are denoted by the same reference numerals, and the descriptionthereof will be omitted. As shown in FIG. 14A, accessory interconnects40 are provided in the interlayer dielectric films 8 and 10 in thescribe region 3.

FIG. 14B is a plan view corresponding to the structure shown in FIG.14A. In FIG. 14B, seal rings 4 under the passivation film 11 areschematically represented by bold broken lines. As shown in FIG. 14B, inthe conventional semiconductor device, the seal rings 4 are provided inthe shape of lines along the scribe region 3.

FIG. 15A is a view schematically showing a cross-sectional structure ofthe semiconductor device of the first embodiment shown in FIG. 2A. FIG.15A shows peripheral parts of two chip regions 102 sandwiching thescribe region 103. In FIG. 15A, some components are not shown andcomponents also shown in FIG. 2A are denoted by the same referencenumerals, and the description thereof will be omitted. As shown in FIG.15A, accessory interconnects 140 are provided in the interlayerdielectric films 107 and 108 in the scribe region 103.

FIG. 15B is a plan view corresponding to the structure shown in FIG.15A. In FIG. 15B, the seal rings 104 including the cap layers 125 attheir tops are schematically represented by bold solid lines. As shownin FIG. 15B, in the semiconductor device of the first embodiment, theseal rings 104 are provided in the shape of lines along the scriberegion 103.

FIGS. 16A through 16C show planar structures of variations of thesemiconductor device of the third embodiment, in comparison with theplanar structure of the conventional semiconductor device shown in FIG.14B and the planar structure of the semiconductor device of the firstembodiment shown in FIG. 15B. In FIGS. 16A through 16C, the seal rings104 are also schematically represented by bold solid lines.

The planar structure shown in FIG. 16A is characterized in that each ofthe seal rings 104 is in the shape of a rectangular wave when viewedfrom above the substrate 101 (i.e., the passivation film 109).

The planar structure shown in FIG. 16B is characterized in that each ofthe seal rings 104 is in the shape of a triangular wave when viewed fromabove the substrate 101.

The planar structure shown in FIG. 16C is characterized in that aplurality of projections extend toward the scribe region 103 from a sideof each of the seal rings 104. Specifically, each of the seal rings 104has a plurality of projections extending vertically to the direction inwhich the scribe region 103 runs.

The cross-sectional structures of the semiconductor devices associatedwith the respective structures shown in FIGS. 16A through 16C aresimilar to that of the first embodiment shown in FIG. 15A or 2A exceptthat the position of the seal rings 104 shifts horizontally or the widthof the seal rings 104 changes depending on the position at which thecross-sectional structure is observed.

Methods for fabricating the respective semiconductor devices associatedwith FIGS. 16A through 16C are similar to that of the first embodiment(shown in FIGS. 4A through 4D, 5A through 5C and 6A through 6C) exceptthat mask patterns for forming seal rings differ among FIGS. 16A through16C.

In the semiconductor device having a seal ring structure of thisembodiment shown in any one of FIGS. 16A through 16C, the seal rings 104serving as bathers for protecting the chip regions 102 are provided notonly in the direction parallel to the direction in which the scriberegion 103 runs but also in a direction vertical or diagonal to thatdirection. Accordingly, it is possible to prevent impact and stresscaused by contact of a dicing blade with a film such as the passivationfilm 109 during dicing and cracks and the like occurring in the wafer(substrate 101) by the impact and stress, from propagating along thesides (the sides facing the scribe region 103) of the seal rings 104.

FIG. 17A is a view schematically showing a cross-sectional structure ofthe semiconductor device of the second embodiment shown in FIG. 8A. FIG.17A shows peripheral parts of two chip regions 202 sandwiching thescribe region 203. In FIG. 17A, some components are not shown andcomponents also shown in FIG. 8A are denoted by the same referencenumerals, and the description thereof will be omitted. As shown in FIG.17A, accessory interconnects 240 are provided in the interlayerdielectric films 207 and 208 in the scribe region 203.

FIG. 17B is a plan view corresponding to the structure shown in FIG.17A. In FIG. 17B, the seal rings 204 a and 204 b including the caplayers 225 a and 225 b at their tops are schematically represented bybold solid lines. As shown in FIG. 17B, in the semiconductor device ofthe second embodiment, the seal rings 204 a and 204 b are provided inthe shape of two lines along the scribe region 203.

FIGS. 18A through 18C show planar structures of variations of thesemiconductor device of this embodiment, in comparison with the planarstructure of the semiconductor device of the second embodiment shown inFIG. 17B. In FIGS. 18A through 18C, the seal rings 204 a and 204 b arealso schematically represented by bold solid lines.

The planar structure shown in FIG. 18A is characterized in that each ofthe seal rings 204 b near the scribe region 203 is in shape of arectangular wave when viewed from above the substrate 201 (i.e., thepassivation film 209).

The planar structure shown in FIG. 18B is characterized in that each ofthe seal rings 204 b near the scribe region 203 is in the shape of atriangular wave when viewed from above the substrate 201.

The planar structure shown in FIG. 18C is characterized in that aplurality of projections extend toward the scribe region 203 from a sideof each of the seal rings 204 b near the scribe region 203.Specifically, each of the seal rings 204 b has a plurality ofprojections extending vertically to the direction in which the scriberegion 203 runs.

The cross-sectional structures of the semiconductor devices associatedwith the respective structures shown in FIGS. 18A through 18C aresimilar to that of the second embodiment shown in FIG. 17A or 8A exceptthat the position of the seal rings 204 b shifts horizontally or thewidth of the seal rings 204 b changes depending on the position at whichthe cross-sectional structure is observed.

Methods for fabricating the respective semiconductor devices associatedwith FIGS. 18A through 18C are similar to that of the second embodiment(shown in FIGS. 9A through 9D and 10A through 10C) except that maskpatterns for forming seal rings differ among FIGS. 18A through 18C.

In the semiconductor device with a seal ring structure of thisembodiment shown in any one of FIGS. 18A through 18C, the followingadvantage is obtained in addition to the advantages of the secondembodiment obtained by the double seal ring structure. That is, the sealrings 204 b near the scribe region 203 out of the seal rings 204 a and204 b serving as bathers for protecting the chip regions 202 areprovided not only in the direction parallel to the direction in whichthe scribe region 203 runs but also in a direction vertical or diagonalto that direction. Accordingly, it is possible to prevent impact andstress caused by contact of a dicing blade with a film such as thepassivation film 209 during dicing and cracks and the like occurring inthe wafer (substrate 201) by the impact and stress, from propagatingalong the sides (the sides facing the scribe region 203) of therespective seal rings 204 b.

In the seal ring structures (double structures) of this embodiment shownin FIGS. 18A through 18C, the seal rings 204 a in the shape of lines ina plan view and the seal rings 204 b in a shape other than the lineshape in the plan view are combined. Alternatively, the seal rings 204 aand 204 b may be in the same shape or in different shapes other than theline shape in a plan view. Alternatively, a seal ring structure whichincludes three or more seal rings and in which at least the outermostseal ring is in a shape other than the line shape in a plan view may beused. However, if the seal ring structure includes seal rings in ashape/shapes other than the line shape in a plan view or includes threeor more seal rings, the widths of the seal rings occupy a large part ofthe width of a semiconductor device (i.e., semiconductor chip), so thatthis structure might be disadvantageous in miniaturization ofsemiconductor devices. Therefore, it is preferable to use a double sealring structure in which a seal ring in the shape of a line in a planview and a seal ring in a shape other than the line shape in the planview are combined, as the seal ring structures of this embodiment shownin FIGS. 18A through 18C, respectively.

As described above, in the foregoing embodiments of the presentinvention, a seal via constituting a seal ring and a dual damasceneinterconnect structure in a chip region are formed through an interlayerdielectric film by the same process and the seal via is continuous inthe film. Therefore, the seal via penetrates the interlayer dielectricfilm without a “junction”. Accordingly, the number of “junctions” isreduced in the entire seal ring structure. This further prevents animpurity or the like from entering through “junctions”, as compared to aseal ring structure including a large number of “junctions”. As aresult, the strength of the seal ring structure is enhanced. That is, itis possible to prevent impact from propagating into a chip region duringdicing. In addition, it is also possible to prevent an impurity or thelike from entering the chip region from the outside.

In the foregoing embodiments of the present invention, the structure inwhich a cap layer is provided at the top of a seal ring, the structurein which a seal via constituting a seal ring is divided into branches,the structure in which a seal via is formed simultaneously withformation of a dual damascene structure in a chip region, and thestructure in which a plurality of seal rings surround a chip region, areused. These structures further ensure prevention of damage to a chipregion or prevention of damage to part of the chip region when a waferis diced into chips along a scribe region. Accordingly, it is possibleto prevent impact on the scribe region during dicing from propagatinginto the chip region, so that an IC, interconnect layers and others inthe chip region are not damaged. As a result, the yield in manufacturingsemiconductor devices (chips) is enhanced and high-precision chips areobtained.

In the foregoing embodiments of the present invention, a seal ringstructure is provided in a peripheral part of a chip region (part of thechip region near the boundary between the chip region and the scribedregion.) Alternatively, the seal ring structure may be provided in partof the scribed region (part of the scribe region near the boundarybetween the scribed region and the chip region) which will remain as anend portion of a semiconductor device (semiconductor chip) after dicing.

What is claimed is:
 1. A semiconductor device, comprising: a substrateincluding a chip region; a plurality of dielectric films formed over thesubstrate; seal rings formed in a peripheral part of a chip region, theseal rings including a first seal ring and a second seal ring, the firstseal ring surrounding the second seal ring, the first seal ring and thesecond seal ring both provided through at least one of the plurality ofdielectric films in the peripheral part of the chip region; aninterconnect formed in the plurality of dielectric films in the chipregion; a first dielectric film included in the plurality of dielectricfilms and being in contact with an upper surface of the interconnect; afirst opening provided in the first dielectric film and formed on thefirst seal ring; a second opening provided in the first dielectric filmand formed on the second seal ring; a third opening provided in thefirst dielectric film and formed on the interconnect; a first cap layerdisposed in the first opening and being in contact with the first sealring; a second cap layer disposed in the second opening and being incontact with the second seal ring; and a pad electrode disposed in thethird opening and being in contact with the interconnect, wherein theplurality of dielectric films includes a second dielectric film and athird dielectric film, both of the second and third dielectric films areformed between the substrate and the first dielectric film, at least oneof the first and second seal rings includes one or more first seal viasin the second dielectric film and one or more second seal vias in thethird dielectric film, the second dielectric film is formed between thesubstrate and the third dielectric film, and a length of one of thesecond seal vias is larger than a length of one of the first seal vias.2. The semiconductor device of claim 1, wherein a thickness of a centerof the first cap layer in a depth direction is larger than a thicknessof the first dielectric film in the depth direction.
 3. Thesemiconductor device of claim 1, wherein a distance between an end ofthe first cap layer located further from the second seal ring and apoint on the second seal ring contacting the second cap layer is greaterthan a distance between an end of the first seal ring located furtherfrom the second seal ring and the point on the second seal ring.
 4. Thesemiconductor device of claim 1, wherein a width of the first cap layeris larger than a width of the first opening.
 5. The semiconductor deviceof claim 1, wherein a width of the second cap layer is larger than awidth of the second opening.
 6. The semiconductor device of claim 1,wherein a distance from an interface between the first cap layer and thefirst seal ring to the substrate is substantially equal to a distancefrom the upper surface of the interconnect to the substrate.
 7. Thesemiconductor device of claim 1, wherein the plurality of dielectricfilms includes a fourth dielectric film formed between the substrate andthe first dielectric film and being in contact with the first dielectricfilm, and a width of the first cap layer is larger than a width of thefirst seal ring formed in the fourth dielectric film.
 8. Thesemiconductor device of claim 1, wherein at least one of the first andsecond seal rings includes two or more seal vias in a same layer.
 9. Thesemiconductor device of claim 1, wherein a width of one of the secondseal vias is larger than a width of one of the first seal vias.
 10. Thesemiconductor device of claim 1, wherein the first and second seal ringsinclude at least one material selected from the group consisting of W,Al and Cu.
 11. The semiconductor device of claim 1, wherein the firstand second cap layers include Al.
 12. The semiconductor device of claim1, wherein the first seal ring is an outermost seal ring of the sealrings.
 13. The semiconductor device of claim 1, wherein the first andsecond seal rings and the first and second openings continuouslysurround the chip region.
 14. The semiconductor device of claim 1,wherein the interconnect is one of a plurality of interconnects formedin the plurality of dielectric films in the chip region, and theinterconnect is the closest of the plurality of interconnects to thefirst dielectric film.
 15. The semiconductor device of claim 1, whereinthe third dielectric film is thicker than the second dielectric film.16. The semiconductor device of claim 1, wherein the first dielectricfilm includes silicon and nitrogen.
 17. The semiconductor device ofclaim 16, wherein the first dielectric film includes silicon nitride.18. The semiconductor device of claim 1, wherein the first cap layer isan outermost cap layer of cap layers formed on the first dielectricfilm.
 19. The semiconductor device of claim 1, wherein the one or moresecond seal vias are the closest of a plurality of seal vias to thefirst dielectric film, and at least one of the first and second sealrings includes only two second seal vias when viewed in a cross-sectiontaken in a thickness direction of the semiconductor device.
 20. Thesemiconductor device of claim 19, wherein the at least one of the firstand second seal rings includes two or more seal vias directly below atleast one of the only two second seal vias.